Adjustable-arm protractor.



H. B. HILL.

ADJUSTABLE ABM PBOTRAOTOR.

APPLICATION FILED 1330.19, 1911.

15023,?38. Patented Apr. 16, 1912.

WITNESSES INVENTOR ATTY.

oLumau PLANOGRAPH C0 WASHINGTON. D. c.

HARRISON B. HILL, OF EAST PROVIDENCE, RHODE ISLAND.

ADJUSTABLE-ARM PBOTRACTOR.

Specification of Letters Patent.

Application filed December 19, 1911.

Patented Apr. 16, 1912. Serial No. 666,852.

To all whom it may concern Be it known that I HARRISON B. HILL, a citizen of the United t-ates, residing at East Providence, in the county of Providence and State of Rhode Island, have invented a new and useful Adjustable-Arm Protractor, of which the following is a specification.

The purpose of my invention is to provide a protractor adapted for use, either side uppermost, in conjunction with a T-square, and which can be easily and readily adjusted and set at any desired angle; be convenient for dividing circles or duplicating angles; and which may take the place of the 45 and 60 triangles ordinarily used by draftsmen.

My invention consists in the construction, combination and arrangement of parts hereinafter described, and shown in the accompanying drawings, in which:

Figure 1 is a perspective view, showing my invention in use in conjunction with a drawing board and T-square. Fig. 2 is a plan view of my protractor, adjusted at an angle of 30. Fig. 3 is an edge view of my protractor, the free ends being broken away. Fig. 4 is a side elevation, enlarged, partly in section, and with parts broken away. Fig. 5 is a section on line 55 of Fig. 2. Fig. 6 is a section on line 66 of Fig. 4.

Similar reference letters refer to similar parts throughout the drawings.

Referring to the drawings: A represents the stationary arm of my protractor and B the movable arm having its rear end pivotally connected to the rear end of the arm A, the opposite end of each arm being free. Said arm A is provided with a horizontally directed perforation a located midway between the upper and under faces of'said arm and near said rear end. I cut away the inner portion of said arm A adjacent said rear end to form a longitudinally extending recess or niche a disposed perpendicularly to and opening into said perforation a In said niche a I seat a longitudinally slidable clamp 0 having a centrally located longitudinally directed perforation adapted to receive an adjusting screw 0 tapped into the arm A and adapted to lock said clamp in any fixed position. I also cut away the inner portion of the body of the arm B for a distance from its rear end to form a longitudinally extending niche 6 arranged to register with the niche a of the arm A when the arms A and B are shut together and thereby constitute a containing chamber for the clamp and its adjusting screw. To the inner side of the arm B and extending laterally therefrom I secure a quadrant or graduated arc, cl, arranged and adapted for operation through the perforation a as the arm B is moved toward or from the arm A. The clamp c is arranged and adapted to engage with the inner edge of the quadrant and thereby lock it in its adjusted position.

In the practical operation of my invention the protractor is laid upon a drawing board, table or the like, with the arm A parallel with and in contact with one edge of the T- square, and the quadrant (Z lying across the upper face of the T-square. The arm B is moved laterally until the desired angle is described, when the clamp 0 is moved longitudinally into contact with the inner edge of the quadrant and there locked by the adjusting screw, 0 to prevent further movement of the arm B. The quadrant cl passing through the arm A in the axial line of the latter permits the arm A to rest evenly upon the drawing board, and also allows the protractor to be used with either side up. Furthermore the clamp 0 lies wholly between the planes of the upper and under surfaces of the protractor arms and thus presents no obstruction to the use of the protractor either side uppermost.

I claim:

An adjustable arm protractor comprising a stationary arm provided with a niche formed in its rear inner edge, and with a horizontally directed perforation disposed at right angles to the axial line of said arm perpendicular to said niche and opening into the latter, a movable arm having its rear end pivotally connected to the rear end of said stationary arm and provided with a niche in its rear inner edge arranged and adapted to register with the niche in said stationary arm, a quadrant carried on said movable contact with the edge of said quadrant to arm and extending laterally from the inner lock the protractor arms at any desired edge of said arm and arranged and adapted angle to each other.

to operate through said perforation in said HARRISON B. HILL. stationary arm, and a longitudinally slid- Vitnesses:

able clamp seated in said niche in said sta- PARKER L. MONROE,

tionary arm and arranged and adapted to JOHN L. MARQNEY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, D. C. 

